You can remark to the mother of children of color that you're worried about the "make up" of a particular neighborhood -- that you think the street might be mostly "black" and are wondering if that means "unsafe" -- but if you do, she will likely be offended. And she will not be being "overly sensitive" when blood rushes to her cheeks.
Note that ultimately she doesn't sweat whether you think the neighborhood is too "black," however much she wishes people didn't think like this anymore. She is a pragmatist, and she believes that she cannot change your mind, what happens between you and you. She will be most disturbed by what you say, by the fact that you have managed to miss that her family is multiracial, decided to wonder "black" and "unsafe" in front of her children, and refuse to understand why she is bothered.